Pulse radiolysis studies of dendritic macromolecules with biphenyl peripheral groups and a ruthenium tris-bipyridine core.

Electron-transfer reactions in Fréchet-type dendrimers with biphenyl peripheral groups and a ruthenium core were investigated by pulse radiolysis techniques. Fast electron-transfer rates found in the two ruthenium dendrimers suggest a very efficient electronic coupling between the peripheral donor groups and the core acceptor.

Photochemistry and spectroscopy of "stable organic radicals": steric and electronic effects in intermolecular photoinduced electron transfer.

The intermolecular reactivities of amino-substituted perchlorotriphenylmethyl radicals 1-3 were studied, with particular emphasis on electron transfer (ET) reactions. The natural fluorescence lifetimes and the rates of the electron-transfer quenching were studied with several electron donors and acceptors. Fluorescence quenching studies demonstrate the importance of the redox potentials of the ET pair on the observed steric and electronic properties.

Immunophenotyping using gold or silver nanoparticle-polystyrene bead conjugates with multiple light scatter.

BACKGROUND: The type of antibody-conjugated polystyrene (PS) latex beads for use as light scatter shift agents for targeted lymphocyte populations in whole blood has been expanded to include gold and silver nanoparticle-aminodextran-PS latex bead conjugates with antibodies. The linkers between antibody and colloidal metal were an aminotrithiol ligand or aminodextran polymer molecules. METHODS: A modified flow instrument, including forward light scatter (FS), side light scatter (SS), light scatter at other intermediate angle ranges, LMALS (10-20 degrees ) and UMALS (20-65 degrees ) was used for simultaneous bead probe measurements. A conventional flow cytometer was used in simultaneous bead-fluorescent marker experiments. RESULTS: Two mutually exclusive cell populations, CD4+ and CD8+ lymphocytes, have been simultaneously enumerated in blood by using a mixture of CD4-PS, CD8-Au-PS or CD4-Au-PS, CD8-PS beads, and one laser line, 633 nm, excitation. Similar measurements were made with mixtures of CD4-PS, CD8-Ag-PS or CD4-Ag-PS, CD8-PS beads. Also, simultaneous use of bead and fluorescent markers mixed with whole blood was demonstrated with CD4-PS beads and with the CD4-RD1/CD8-FITC dual marker. CONCLUSIONS: Enumeration of CD4 and CD8 lymphocytes in whole blood by light scatter parameters only compared well with standard analyses with fluorescent markers. In simultaneous bead-fluorescent marker labeling of lymphocytes, the labeled bead had to be mixed first with cells in whole blood.

Tris(3-mercaptopropyl)-N-glycylaminomethane as a new linker to bridge antibody with metal particles for biological cell separations.

Conjugates of nickel beads with CD8 and anti-red blood cell KC16 antibody were prepared by using the aminotrithiolate "spider" ligand, tris(3-mercaptopropyl)-N-glycylaminomethane, in its new function as a linker between the surface of nickel beads and antibody via activation of spider ligand attached to nickel beads with the common, heterobifunctional cross-linker, sulfosuccinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate (sulfo-SMCC). Raw nickel beads were cleaned by either mild sonication in a bath or by stronger probe sonication to remove surface nickel oxide layers, before attachment of the spider ligand. Scanning electron micrographs of the nickel beads before and after probe sonication showed a marked change from a corrugated to a smooth bead surface. Analyses of the supernatants of conjugation mixtures for antibody gave surface densities of 2.5-5.2 mg/m(2) for CD8 and 0.6-12 mg/m(2) for KC16 antibody runs. The antibody-spider-nickel bead conjugates were used in magnetic bead depletions of targeted CD8+ lymphocytes or red blood cells (rbcs) in whole blood of normal donors. For CD8 cell depletions, the undepleted controls and supernatants of depleted samples were analyzed for CD8/CD4 cell populations by flow cytometry with appropriate fluorescent antibody markers. Enumeration of red blood cells, white blood cells (wbcs), and platelets (plts) in undepleted controls and supernatants of depleted samples were carried out on appropriate hematology counters. Whole blood titer results with various lots of either CD8-spider-nickel or KC16-spider-nickel bead conjugates showed varying degrees of depletion ability as indicated by bead-to-cell ratios of 2-32 for CD8 beads and by rbc-to-bead ratios of 1.2-10 for KC16 beads. Moreover, varying degrees of specificity of CD8 beads for CD8+ cells over CD4+ cells and of KC16 beads for rbcs over white blood cells and platelets were observed from the normalized nontargeted cell population figures in undepleted controls versus supernatants of depleted samples.

Directionally aligned helical peptides on surfaces.

Directionally oriented peptide layers 1000 angstroms thick were constructed by polymerization on gold and indium-tin-oxide glass. A key feature is the use of an appropriately functionalized surface on which the initiation sites for polymerization are spaced at distances consistent with the helical diameter of the peptide. Completely helical polyalanine and polyphenylalanine layers have been constructed. The helicity of the polyalanine layer was completely retained after heating at 180 degrees C for 7 days.

The structure at 198 K of (1R,5R,15R,16R)-5-isopropenyl-2-methyl- 1-[N-(trans-2-phenylcyclohexyloxycarbonyl)amino]-2-cyclohexene.

trans-2-Phenylcyclohexyl N-(5-isopropenyl-2-methyl-2-cyclohexan-1-yl) carbamate, C23H31NO2, Mr = 353.50, orthorhombic, P2(1)2(1)2(1), a = 8.813 (2), b = 9.043 (2), c = 25.643 (5) A, V = 2043.6 (8) A3, Z = 4, Dx = 1.15 g cm-3 (198 K), Mo K alpha radiation, lambda = 0.7107 A, mu = 0.6734 cm-1, F(000) = 768, T = 198 K, R = 0.0547 for 1772 reflections [Fo greater than or equal to 4 sigma(Fo)]. Molecules are H-bonded into infinite columns parallel to a. The H bond involves the NH group and the carbonyl O atom of the carbamate moiety with relevant parameters: N11-H11...O13 (related by 1/2 + x, 1/2 - y, - z); N...O 2.910 (5), H...O 2.11 (5) A, N-H...O 159 (4) degrees.

Stereocontrolled synthesis of peptide bond isosteres.

Absolute stereochemical control is employed in the synthesis of isosteres for dipeptide subunits (1; see Fig. 1) in which the amide linkage has been replaced by a trans carbon-carbon double bond. The synthesis affords access to the four stereoisomers of 1 in which R and R' = CH3, including the isostere for D-alanine-D-alanine (D-Ala-D-Ala), 2.